Development and Evolution of the Nervous System 3

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  • Created by: jessica
  • Created on: 18-10-13 09:30

The somatic nervous system has 31 pairs of spinal nerves from the spinal cord and 12 cranial nerves from the brain. The afferent axons carry sensory information from the skin, muscles, joints and viscera into the CNS. These are normally connected to mechanoreceptors, noiceptors and thermoreceptors.  The efferent axons leave the CNS as motor neurons supplying the skeletal muscles. The spinal nerves are mixed containing sensory and motor fibres (exception C1 motor Cx1 sensory). There are only 4 cranial nerves that are mixed. Peripheral nerves are collected into fasciculi and are supported by the endonerium and then surrounded by the perineurium. The autonomic nervous system is the visceral motor nervous system. The target tissues are smooth muscle, cardiac muscle, endocrine/exocrine glands, liver, kidney and adipose tissue. The synapses of autonomic neurons are neuroeffector junctions. ANS has 2 divisions, sympathetic and parasympathetic. Preganglionic neurons of the ANS have cell bodies in cranial nerves or the intermediolateral horn of the thoracic and lumber spinal cord. The myelinated B axons release…


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